Domain-specific experience with CPAN modules for using databases, etc., etc.

For me, 3 was something of a steep learning curve (but one I eventually got over). But 4 is an ongoing journey of discovery! (For example, see my very recent post Re^2: RegEx + vs. {1,}.)

Now, I would definitely recommend that you acquire the latest edition of the Camel Book, but “reading through” is probably not the way to go. Focused reading, targeting any weak areas in the above list, will likely be far more productive.

And don’t neglect other sources of information: Perl documentation, especially the FAQs, comp.lang.perl.misc, and of course PerlMonks! Also don’t be afraid to challenge yourself. I can’t recommend Higher-Order Perl (free online) by Dominus highly enough in this regard.